The ancient bacteria were found frozen in the world's oldest known tracts of ice, the debris-covered glaciers of Antarctica.

"We think that they were pretty much locked in a frozen, inanimate state for that period of time," said lead study author Kay Bidle, a marine microbiologist at Rutgers University in New Brunswick, New Jersey.

It's also possible that some of the microbes were capable of maintaining their metabolism within tiny droplets of water suspended in the ice, Bidle said.

Bidle and colleagues retrieved and revived two samples of bacteria from the glacial ice. The first was a hundred thousand years old, and the second was around eight million years old.

The eight-million-year-old bacteria were alive, but barely.

Their genes were severely damaged from long exposure to cosmic radiation, which is higher at Earth's poles.

The radiation bombarded the bacteria's DNA with high-energy particles, which broke apart the DNA's chemical bonds and hacked it into shorter pieces.

Big Bacterial Thaw

Most of the bacteria in the samples probably blew over from African deserts, said study co-author Paul Falkowski, a biochemist at Rutgers.

Once the bacteria landed on the glacier's snowy surface, they were compressed with the snow to form ice.